Oh wow, poll results actually surprised me.. I mean I know lots of younger people play games, but didn't expect to see my age bracket as less than 4%, heck, those of us in our thirties grew up right as video game consoles were booming in the 80's
Well, consider that people in their 30s and 40s tend to live somewhat busy lives, so unless you work in an IT job, time to spend on forums is somewhat limited and often shared with gaming time. Younger people tend to have more time (they don't feel that way, but nevertheless), so forum audiences may generally be younger than the audience playing the games.
Also, thinking back to the 80s, when I got my first computer in 1985 (I was thirteen then), only three other kids in my class also had a computer. That was only about 10%, though consoles had started to emerge and move into a more mainstream awareness. After 1990, everyone I knew had a computer, but I had started working in the IT field then, so that's not surprising. This was in Germany, so maybe subtract a year or two for the US.